1. Field of the Invention
This invention relates generally to the field of thin label applicators, and more specifically, to a device for removing pressure-sensitive, very thin, subsurface printed labels from a label web and precisely applying the labels to articles, such as PCMCIA memory cards, carried on a linearly moving, reciprocating shuttle.
2. Description of the Related Art
Numerous types of label applicator devices are available and used in various industries for applying adhesive-backed labels to articles. The labels are typically provided on rolls of label tape on which the individual labels are spaced apart and removably attached to the tape, also referred to as a web or release liner, by an adhesive coated surface of the labels. Additionally, the labels may be preprinted on their nonadhesive, outwardly facing surfaces. A roll of label-bearing web is mounted on a reel and passed through a device which removes the individual labels from the release liner and applies them to articles passing by the device on a continuously moving conveyor. The empty tape is subsequently wound onto a take-up reel.
These mechanisms utilize various types of arrangements for removing the labels from the web, moving the labels into a labeling position and applying the labels to unlabeled articles. The most common method of removing adhesive-backed labels from a web is to bend the web away from the label so as to form a small radius shear line between the label and the web. The label is peeled off along the shear line by pulling the web and the label away from each other. Typically, mechanisms employing this procedure are provided with a surface around which the label bearing web is directed. As the web is passed around the surface, an acute angle is formed between the surface and the label such that the leading edge of the label passing over the surface is disengaged from the release liner. The adhesive coated surface of the leading edge is then contacted with the surface of a moving article carried on the conveyor such that further movement of the article by the conveyor peels the remainder of the label from the web and transfers it onto the article. A wiper or roller may also be employed to provide pressure to the nonadhesive side of the label, thus ensuring that the label is securely fastened to the article.
Alternatively, the label may be peeled completely from the web by a transfer device which subsequently moves the label into contact with an article moving along the conveyor. Typically, the transfer device draws a vacuum so that the nonadhesive coated surface of the label can be held against a vacuum screen or pad during transfer from the label pick-up position to the label dispensing position. The transfer device will engage the leading edge of the label as it is separated from the web. Further, movement of the transfer device may be used to separate the trailing portion of the label from the web. Once the transfer device has moved a label into contact with an article, the vacuum will be released so that the label adheres to the article. Additionally, a positive air stream may be applied to project the label onto the article.
These labeling mechanisms attempt to combine high application speeds, i.e., the rate at which labels can be applied to the articles, with accurate positioning of the labels on the articles. Unfortunately, application speed often must be traded for accuracy of placement of the labels. Positional discrepancy in label placement is common in labeling mechanisms, such that labels are not applied exactly to the portion of the article intended to receive the labels. This is especially true of labeling mechanisms used in combination with conveyor systems for moving articles. Although such discrepancies are satisfactory for large articles which do not require accurate label placement, small articles, such as memory cards, circuit boards, etc. require much more accurate placement. For example, Personal Computer Memory Card Industry Association (PCMCIA) cards are emerging for use in a full range of low-power, small-form, factor applications for personal computers. Because these cards are approximately the size of a credit card, label placement must be very accurate. Those skilled in the art recognize that the smaller the labels and the smaller the articles to be labeled, the greater the significance of accurate placement by the labeling device.
One method used to lessen accuracy discrepancies has been to employ sensors to regulate the speed of various components of label transfer systems. These sensors have been used to detect the speed of the label-bearing web as it moves through the system, the position of labels on the web, the leading edges of labels as they are detached from the web, the speed of transfer devices, the presence of labels and/or articles to be labeled and the speed of conveyors used to move articles. However, the effectiveness of these sensors has been limited because they fail to synchronize the transfer device and the conveyor based on the position of the label on the transfer device and the position of the article on the conveyor. Further, mechanisms which utilize sensors in this manner are not easily adapted for use with labels of varying size.
Therefore, a thin label applicator which utilizes a reciprocating article delivery system is desirable. The position of this system should be adjustable so that the positions of the article delivery system and the transfer device can be synchronized based on the position of labels carried on the transfer device. Further, a mechanism for adjusting the articles held by the article delivery system so that accuracy of label placement can be increased is also desirable. Lastly, the mechanism should rapidly dispense labels while at the same time maintaining a high degree of accuracy with respect to label placement.